在Java中，如何手动关闭Kafka连接？

import org.apache.kafka.clients.consumer.Consumer;
import org.apache.kafka.clients.consumer.ConsumerConfig;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.KafkaConsumer;
import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.Producer;
import org.apache.kafka.clients.producer.ProducerConfig;
import org.apache.kafka.clients.producer.ProducerRecord;

import java.util.Collections;
import java.util.Properties;

public class KafkaConnectionExample {

    public static void main(String[] args) {
        // Kafka producer configuration
        Properties producerProps = new Properties();
        producerProps.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "kafka_servers");
        producerProps.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringSerializer");
        producerProps.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringSerializer");

        // Create Kafka producer
        Producer<String, String> producer = new KafkaProducer<>(producerProps);

        // Send messages
        producer.send(new ProducerRecord<>("my_topic", "message_key", "message_value"));

        // Close Kafka producer connection
        producer.close();

        // Kafka consumer configuration
        Properties consumerProps = new Properties();
        consumerProps.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "kafka_servers");
        consumerProps.put(ConsumerConfig.GROUP_ID_CONFIG, "my_group");
        consumerProps.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
        consumerProps.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");

        // Create Kafka consumer
        Consumer<String, String> consumer = new KafkaConsumer<>(consumerProps);

        // Subscribe to topic
        consumer.subscribe(Collections.singleton("my_topic"));

        // Consume messages
        ConsumerRecords<String, String> records = consumer.poll(100);
        records.forEach(record -> System.out.println("Received message: " + record.value()));

        // Close Kafka consumer connection
        consumer.close();
    }
}